Gain insights on the acceptable modifications of color and other additive concentrates to plastic materials at the molder for finished plastic parts used within electrical equipment.
FAQs
- If a UL Recognized base resin listing states “ALL” colors, does it really mean ALL colors?
Yes, If the recognition mentions “ALL” colors, the material manufacturer can produce the base resin in any color. “ALL” color recognitions are initially tested unpigmented, the most heavily pigmented organic and inorganic pigments, and certain color pigments known to affect flammability characteristics, such as carbon black. The “ALL” color recognition holds good as long as the produced colors are less than or equal to the maximum limits initially tested.
- If a UL Recognized base resin listing states “ALL” colors, does it mean it can be used with any UL Recognized or non-Recognized colorant?
“ALL” color recognition of base resin includes “unpigmented/natural” color as well. Molders/fabricators can modify this recognized unpigmented/natural colored material by using a UL Recognized color concentrate only. Molders/fabricators cannot add colorants with a UL Recognized unpigmented resin unless the color was tested with the specific resin and found to not adversely affect the flammability of the material. The exception to this is the use of UL Recognized colorants that have been classed HB or better when used with a Recognized resin classed HB of the same generic type.
- In the UL Product iQ® database, some colorants are listed with specific resins, whereas others are listed with generic resin families. What is the reason for this?
UL Recognized colorants that have been classed HB or better may be used with a Recognized resin classed HB (the least severe flame class in the flame rating hierarchy) from the same generic type and do not require testing with a specific resin. UL Recognized colorants that have been classed V-2 or better must be evaluated with a specific resin. Please see the Flammability section of the Guide Information page for the flame rating hierarchy.
- If a UL Recognized colorant with HB rating is used with a base resin with V-2 or better flammability rating, does it affect the flammability rating of the base resin?
This case would need to be evaluated to determine whether the flammability rating is adversely affected.
- If a colorant that is not outdoor rated (f1) is used with a UL Recognized base resin rated f1, does it affect the f1 rating of the base resin?
Outdoor rating (f1) on a UL Recognized base resin is the proprietary information of the base resin manufacturer. Any modification of such a base resin by the molder/fabricator by the addition of colorant must be evaluated for all the applicable properties as determined by the end-product engineer. Parts may be investigated to the applicable UL Standards for end-use products and/or the requirements outlined in UL 746C, the Standard for Polymeric Materials — Use in Electrical Equipment Evaluations. The color concentrate program under QMQS2 evaluates the modification of the base resin with color concentrate for flammability only.
Colorants themselves would not be outdoor rated. The outdoor rating is based on the resin and the specific colorant’s ability to maintain the flame rating and a percentage of the initial strength and impact after water immersion and/or exposure to UV radiation. All colorants affect the resin's outdoor suitability, and the addition of a colorant to a specific base resin would need to be evaluated.
- Can an end-product manufacturer or molded-parts fabricator use non-UL Recognized colorant with UL Recognized resins?
No, molders/fabricators cannot use non-UL Recognized colorants with UL Recognized resins.
- Can an end-product manufacturer or molded-parts fabricator use a UL Recognized colorant rated HB to be used with a specific generic family only (for example, polycarbonate) with a different base resin (for example, nylon)?
No, the UL Recognized colorant classed HB with a specific generic would have to be used with the same generic type only.
- Is it acceptable to exceed the maximum let-down ratio of a UL Recognized colorant?
No, molders and fabricators may only dry-blend in a let-down ratio that is equal or less than the maximum let-down ratio.
- What is the difference between dry-blending and hot-compounding base resins with colorants?
With hot-compounding, the resin and the colorant are heated and blended together and then processed, adding additional heat history to the resin.
With dry-blending, the base resin and colorants are mixed without heating and then processed.
- Is it acceptable for a molder/extruder to first hot-compound a base resin with a rated colorant to achieve desired color mixture and then pelletize and ship to end-product manufacturers for final molding? If not, is there a way to evaluate the process?
No, UL 746D, the Standard for Polymeric Materials — Fabricated Parts, clause 1.4, states that this program is not intended for adding colorants or additives using hot-compounding techniques that subject the material to additional heat history and then shipping pellets as finished parts. In order to evaluate the process, you would need to open a QMFZ3 unlisted component file.
Additional information:
There is a proposal being worked out by the UL 746 Technical Committee to address reprocessing, for which a major concern is the additional heat history with repeated blending of reprocessed material.
- If a base resin has been certified for 100% regrind, is it then acceptable to first hot-compound it with a rated colorant to achieve desired color mixture and then pelletize and ship to end-product manufacturers for final molding?
This falls under the scope of reprocessing, where the molding scrap such as regrind is converted into pellets using an extruder after hot-compounding the scrap with a colorant, and the pellets are used for final molding. Currently, there is a Certification Requirements Decision (CRD) under UL 746D for reprocessed plastics and the UL 746 Technical Committee is working toward incorporating these requirements into the UL 746D Standard.
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